Heating boiler

ABSTRACT

D R A W I N G THE INVENTION RELATES TO A HEATING BOILER OF THE TYPEHAVING A COMBUSTION CHAMBER, A ROTARY BURNER, AN AIR INLET FOR COMBUSTION AIR, AND A VENT WHICH IS CONNECTABLE TO A CHIMNEY. A DISADVANTAGE OF PRIOR ART BOILERS OF THIS TYPE IS THAT THE AIR INLET AND VENT ARE SO ARRANGED THAT ATMOSPHERIC DRAUGHT CONDITIONS CAUSES AIR TO FLOW THROUGH THE COMBUSTION CHAMBER PROPER DURING TIMES WHEN THE BURNER IS NOT OPERATING AND THEREBY CAUSES COOLING OF THE WALLS OF THE BOILER. THIS AIR EITHER FLOWS FROM THE CHIMNEY THROUGH THE COMBUSTION CHAMBER TO THE AIR INLET PIPE, OR VICE VERSA. THE INVENTION INVOLVES AN ARRANGEMENT BETWEEN THE AIR INLET PIPE AND THE CHIMNEY VENT SO THAT THE MOVING AIR IS SHUNTED FROM ONE OF THESE ELEMENTS TO THE OTHER ACROSS THE UPPER PART OF THE COMBUSTION CHAMBER WHEN THE BURNER IS NOT OPERATING. THIS CAUSES THE AIR TO BYPASS THE COMBUSTION CHAMBER PROPER AND THE AIR THUS DOES NOT COME INTO COOLING CONTACT WITH THE COMBUSTION CHAMBER WALL EXCEPT FOR THE UPPER PORTION THEREOF. WHEN THE UNIT IS OPERATING THE ROTARY BURNER CAUSES A CIRCULATORY MOVEMENT OF THE AIR WHICH CAUSES THE RELATIVELY COOL INLET AIR TO BE DRAWN DOWNARDLY TO THE ROTARY BURNER THROUGH THE CENTER OF THE COMBUSTION CHAMBER AWAY FROM THE BOILER WALL, AND CAUSES THE HOT COMBUSTION GASES TO FLOW UPWARDLY IN CONTACT WITH THE BURNER WALL TO THE CHIMNEY VENT.

Feb. 9, 1971 H. o. LERRIS HEATING BOILER Filed March 25, 1968 United States Patent 01 hoe 3,561,899 Patented Feb. 9, 1971 3,561,899 HEATING BOILER Hans 0. Lerris, Nordborg, Denmark, assignor to Danfoss A/S, Nordborg, Denmark, a company of Denmark Filed Mar. 25, 1968, Ser. No. 715,685 Int. Cl. F23d 11/04 US. Cl. 431-168 8 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a heating boiler of the type having a combustion chamber, a rotary burner, an air inlet for combustion air, and a vent which is connectable to a chimney. A disadvantage of prior art boilers of this type'is that the air inlet and vent are so arranged that atmospheric draught conditions causes air to fiow through the combustion chamber proper during times when the burner is not operating and thereby causes cooling of the walls of the boiler. This air either flows from the chimney through the combustion chamber to the air inlet pipe, or vice versa.

The invention involves an arrangement between the air inlet pipe and the chimney vent so that the moving air is shunted from one of these elements to the other across the upper part of the combustion chamber when the burner is not operating. This causes the air to bypass the combustion chamber proper and the air thus does not come into cooling contact with the combustion chamber wall except for the upper portion thereof.

When the unit is operating the rotary burner causes a circulatory movement of the air which causes the relatively cool inlet air to be drawn downwardly to the rotary burner through the center of the combustion chamber away from the boiler wall, and causes the hot combustion gases to flow upwardly in contact with the burner wall to the chimney vent.

This invention relates to a heating boiler having a pipe feeding air to the burner and a vent leading to the chimney. The expression heating boiler is here intended to include all heating equipment operating with a burner for gaseous, liquid or pulverized fuel, irrespective of whether the boiler serves as a furnace for direct space-heating, heats the hot water in a central-heating system, or performs any other function. Perferably, however, the units concerned are small ones as used principally for private purposes.

With heating boilers of this kind, there occurs the disadvantage that during periods when the boiler is not operating, air is sucked in by the chimney draught. The air flows through the boiler space and cools it down, so that undesired losses in energy occur. A further disadvantage occurs particularly in the case of such boilers wherein a certain stability of the flame is important, e.g., in the case of a vaporizing burner. Here, variations in the draught conditions can have a considerable effect upon the stability of the flame. The draught conditions however change very often during normal operation.

The object of the invention is to provide a heating boiler which suffers smaller losses and enables greater stability of the flame to be obtained.

According to the invention, this object is achieved by the air feed pipe being substantially directly in communication with the vent at least during the peroids when the boiler is not operating.

In this way, the air does in fact continuously flow through the chimney, but since it is not passed through the boiler space during the non-operative periods, it cannot extract any heat therefrom. It is even possible to keep the air feed pipe constantly in direct communication with the vent, steps of course being taken to enable the burner nevertheless to receive sufiicient air for combustion. In this way, variations in the chimney draught are offset by the air supplied without the flame being necessarily affected thereby.

A very advantageous solution of this kind consists in arranging the mouth of the air feed pipe near the vent in the boiler space, a circulatory current being obtainable in the boiler space during the running period of the boiler, which current has a pressure gradient from the mouth of the pipe to the burner. This circulatory current carries that part of the air required for combustion to the burner, but prevents neither the removal of the combustion gases through the vent nor direct pressure equalization between the air feed pipe and the vent.

For producing the circulatory current, use can be made of a known rotary burner which, as a vaporizing burner, is of optimum efliciency for a given flame stability.

Expediently, the rotary burner is provided with vanes for reinforcing the circulatory current. While it is known to fit blades on the rotary burner which suck the combustion air from the outside, the vanes in question here must be so arranged that they drive the gases already present in the boiler.

In a preferred embodiment, the mouth of the air feed pipe is disposed coaxially with the rotary burner at the opposite end of the boiler space. Preferably, the vent surrounds the mouth of the air feed pipe likewise concentrically. In this manner, the new air is fed in the middle, whilst the hot gases of combustion sweep the wall of the boiler. New air and extracted gases do not interfere with each other. The cold new air does not come into contact with the walls of the boiler; rather, it is preheated by ra diation as well as by partially mixing with the circulating gases of combustion.

Reinforcement of the circulatory flow can be achieved by covering the end of the boiler space opposite the rotary burner with a plate extending to the vent and if required to the opening of the air feed pipe.

It is also advantageous in many cases if the air feed pipe projects through the rotary burner and the boiler space to a point close to the opposite end. The pipe forms a guide for the circulatory current, so that losses due to eddying can be reduced. In order to prevent excessive heating of the air during the inoperative periods, the pipe can be insulated.

The invention will now be explained in more detail by reference to two embodiments illustrated in the drawing, wherein:

FIG. 1 shows a schematic longitudinal section through a heating boiler and its air feed, seen from above, and

FIG. 2 is a similar illustration of a heating boiler and its air feed, seen from below.

In FIG. 1, a boiler space 1 is defined by a cylindrical boiler wall 2, and by a rotary burner 3 at the bottom, and an annular plate 4 at the top. The mouth 5 of an air feed pipe 6 projects through the plate. Located between the outer circumference of the plate 4 and an outer limiting wall 7, is an annular vent 8 leading to the chimney. Fuel oil is introduced, by way of a pipe 9, into the cone of the rotary burner 3. The rotary burner has vanes 10 projecting into the boiler space and can be driven in the normal way by means of an electric motor, not illustrated.

When the boiler is not in operation, air entering by way of the feed pipe 6 flows over the lower side of the plate 4 directly to the vent 8. It does not therefore fully cool the boiler walls 2.

In operation, the rotary burner 3 sets up a circulatory current 11 since, due to the centrifugal effect at the outer circumference of the boiler space :1, it produces excess pressure (represented by plus signs) and a negative pressure (represented by minus signs) in the region of the axis of the boiler. Consequently, air is sucked out of the mouth 5 and passed to the burner. Without any hindrance thereby, gases of combustion can flow away through the vent 8. Changes in the pressure conditions in the chimney can thereby be equalized between the mouth 5 and the vent 8 without the circulatory flow being adversely affected thereby. Instead, the conditions in the boiler always remain approximately the same, since the plus values as well as the minus values increase or diminish simultaneously and to roughly the same extent. The conditions illustrated also always suffice to suck air from the atmosphere by way of the pipe 6.

In FIG. 2, the conditions are quite similar. The same reference numerals are used for like parts. In this embodiment, the new air is fed in from below by way of a pipe 12 which projects concentrically through the rotary burner 3 and the boiler space 1. Its mouth 5 is again disposed at the side opposite the rotary burner 3 and, in fact, in the vicinity of the vent 8. The pipe 12 has an insulated Wall 13 so that the new air flowing through during the non-operative periods does not pick up too much heat.

What is claimed is:

1. A heating boiler comprising wall means forming a combustion chamber, a rotary burner disposed at the lower end of said combustion chamber, means cooperating with the upper end of said wall means for form vent means at the upper end of said chamber, and an air inlet pipe extending into said combustion chamber having the 2. A heating boiler according to claim .1 having means for producing a circulatory current in said combustion chamber having a pressure gradient which decreases from said mouth of said inlet pipe to said burner.

3. A heating boiler according to claim 2 wherein said rotary burner produces said circulatory current.

4. A heating boiler according to claim 3 wherein said rotary burner has vanes which contribute to the formation of said circulatory current.

5. A heating boiler according to claim 1 wherein said air inlet pipe mouth is coaxially disposed relative to said rotary burner.

6. A heating boiler according to clam 1 wherein said vent means surrounds said mouth of said air inlet pipe.

7. A heating boiler according to claim 1 wherein said means cooperating with said Wall means to form said vent means has the form of a plate.

8. A heating boiler according to claim 1 wherein said air inlet pipe is insulated, said pipe extending through said rotary burner and said combustion chamber.

References Cited UNITED STATES PATENTS 1,447,385 3/1923 Hardinge 431-168 1,903,195 3/1933 Robinson 431168 2,246,809 6/1941 Miller 43 l--168X 2,483,737 10/1949 Parrish 431-190 mouth thereof disposed at the upper end of said chamber. CHARLES J. MYHRE, Primary Examiner 

